ORA-16047: DGID mismatch between destination setting and standby

[oracle@vmxdb01b ~]$ more /u01/app/oracle/admin/prorcl/bdump/prorcl_arc0_5809.trc
/u01/app/oracle/admin/prorcl/bdump/prorcl_arc0_5809.trc
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
ORACLE_HOME = /u01/app/oracle/product/10.2.0/db_1
System name: Linux
Node name: vmxdb01b.lab.dbaglobe.com
Release: 2.6.18-274.12.1.el5
Version: #1 SMP Tue Nov 29 13:37:46 EST 2011
Machine: x86_64
Instance name: prorcl
Redo thread mounted by this instance: 1
Oracle process number: 16
Unix process pid: 5809, image: oracle@vmxdb01b.lab.dbaglobe.com (ARC0)

*** SERVICE NAME:() 2011-12-18 23:47:14.471
*** SESSION ID:(156.1) 2011-12-18 23:47:14.471
kcrrwkx: nothing to do (start)
Redo shipping client performing standby login
*** 2011-12-18 23:47:14.590 64561 kcrr.c
Logged on to standby successfully
Client logon and security negotiation successful!
Error 16047 attaching to destination LOG_ARCHIVE_DEST_2 standby host 'drorcl'
ORA-16047: DGID mismatch between destination setting and standby
*** 2011-12-18 23:47:14.591 58941 kcrr.c
kcrrfail: dest:2 err:16047 force:0 blast:1
kcrrwkx: unknown error:16047
ORA-16055: FAL request rejected
ARCH: Connecting to console port...
ARCH: Connecting to console port...
kcrrwkx: nothing to do (end)

Root Cause:

Case mis-match between db_unique_name and log_archive_config


alter system set LOG_ARCHIVE_CONFIG='DG_CONFIG=(prorcl,drorcl)';
db_name = prorcl
db_unique_name = PRORCL